Automatic crystal transfer device



Nov. 25, 1941. A. P. BOCK 2,263,155

AUTOMATIC CRYSTAL TRANSFER DEVICE Filed Aug, 2, 1940 WITNESSES: INVENTOR flz gih/ey/Qflo CK.

ATTORNEY Patented Nov. 25, 1941 AUTOMATIC CRYSTAL TRANSFER DEVICE Ashley I. Bock, Catonsville,-Md., assignor to Westinghouse Electric 8; Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 2, 1940, Serial No. 349,762

6 Claims.

This invention relates to vacuum tube oscillators and, more particularly, to oscillators utilizing mechanical vibratile elements for controlling the frequency of oscillations.

Vacuum tube oscillators of the type employing a piezo-electric crystal for controlling the frequency of oscillations are particularly used in radio transmitters, mainly for the increased stability obtained at the operating frequency.

Radio transmitters for broadcasting or police work must at all times be in operating condition and provision must be made to avoid operating failure due to all possible causes. A breakdown of the crystal element will produce such operating failure silencing the transmitter until another crystal can be inserted in place of the faulty one. Although such crystals are generally in a compact mechanical assembly and may be replaced in the same manner as vacuum tubes by merely plugging into a suitable receptacle, considerable time is needed for replacement.

The primary object of this invention is to effect the replacement of crystals in a transmitter with the least possible delay, thereby insuring reliability of continued operation.

Another object of this invention is to effect replacement of a crystal element automatically upon fault developed therein with another crystal similar in its operating characteristics.

A further object of this invention is to control the selection of crystals in a vacuum tube oscillator by the presence of grid current in the circuit.

Other objects and advantages will be apparent in connection with the description of the invention, pointed out in particularity by the appended claims, and taken in connection with the accompanying drawing, in which:

The figure illustrates a schematic circuit arrangement of a vacuum tube oscillator incorporating switching means for crystal transfer in accordance with this invention.

Referring to the drawing, a conventional crystal oscillator is shown comprising vacuum tube I having anode 2, cathode 3 and control electrode 4. The output circuit of the tube between anode 2 and cathode 3 includes the conventional tank circuit comprising inductance 5 and tuning capacity 6 in parallel therewith and the operating voltage source shown by battery I. The input circuit between the grid 4 and cathode 3 includes in series the load resistance 9 and the winding In of relay II. In parallel with the last mentioned circuit elements connected directly between cathode and the high potential side of the load 55 resistance 9 is a piezo-crystal element I2. A capacity I3 is effectively in parallel with the winding I0. The relay includes stationary contacts I4 and I5 and I4 and I5. The armature I6 thereof isbiased by the spring 8 against movement by the plunger I8 and carries moving contacts I1 and I1. One of the moving contacts I! is connected directly to the grid electrode 4, whereas the stationary contact I5 is connected to the cathode through a load resistance I9 which is paralleled by another piezo-electric crystal element 20.

Stationary contacts I4 and I5 connect with indicator lights 20 and 20', respectively. A source of operating voltage for these lights comprise battery 2| and is connected between the junction point of the two indicator lights 20 and 20 and the moving contact I! of the relay I I.

An auxiliary source for operating the winding I 0 includes the battery 22, one terminal of which connects to the cathode 3 and through conductor 23 to the Winding I0 and the other terminal in series with a network including resistor 24 and capacity 25 in parallel therewith to the other terminal of the winding I0. A switch 26 is provided to short-circuit the network and connect the battery 22 directly across the winding III.

In the operation of the crystal transfer, the vacuum tube I, when in an oscillatory condition, produces grid current which flows between cathode 3 and grid 4. Tracing the circuit, it is seen that this current must flow through the load resistance 9 and the winding IU of the relay II. The resistance of the winding is so calculated that the normal grid current produces suflicient magnetizing voltage drop to actuate the relay II in the position which connects the crystal element I2 in the circuit and maintain this connection until for any reason this current should cease to flow. The primary reason for cessation of current flow would be any defect of the crystal I2 whereby the oscillator tube would cease to function. In this case, the winding I0 becomes deenergized and the relay armature is automatically returned by the spring 8 in the second position to complete the circuit to contacts I! and I5 placing thereby the second crystal element 20 and its associated load resistance I9 in the grid circuit. The second crytsal 20 is identical with that of I2 and being transferred almost instantaneously in the circuit upon failure of the first crystal element I2, the tube I will resume producing oscillations at the identical frequency, as previously, with practically unappreciable interruption.

The indicator lights 20 and 20' are for the purthe operator of the transmitter takes cognizance of the fact that the spare crystal has been switched in the circuit and may take the necessary preparations for replacing the defective crystal l2 at any time without interfering with the normal operation of the transmitter.

Each time the transmitter is started, since power supply B2 and B1 are applied simultaneously to actuate carrier, the surge current charging condenser 25 through winding l energizes relay H, and the slow-release characteristic of relay ll holds crystal l2 in the circuit until oscillations build up sufficient grid current to supply magnetizing current for relay I 1!.

Should the operator desire tocut out the automatic transfer feature in order to make adjustments of the transmitter and be unimpeded by the transfer device operating because of adjustments, the switch 26 is closed, thereby locking crystal 12 into the circuit as long as switch 26 is closed.

Resistor 24 is a high value, that passes insufficient current to energize relay II. It provides a path of discharge for condenser 25 upon cessation of carrier, in order to promptly repeat the starting of carrier whenever it becomes necessary for carrier to be initiated and shut off alternately at short intervals.

While the drawing and the description shows a preferred embodiment of the invention, it is to be understood that other circuits in connection with relays of various types may be used without departing from the essence of this invention.

What is claimed is:

1. In an oscillator circuit, a vacuum tube having anode, cathode and control electrodes, an

input circuit between said control electrode and cathode including a mechanical vibratile element, an output circuit between said anode and cathode, switching means for connecting said elementto said input circuit, a second vibratile element and means responsive to current flow in said input circuit for controlling the actuation of said switching means for selectively connecting one 'of said elements to said input circuit.

2. In an oscillator circuit, a vacuum tube having anode, cathode and control electrodes, an input circuit between said control electrode and cathode including a first mechanical vibratile element, an output circuit between said anode and cathode, switching means for connecting said element to said input circuit, a second vibratile element and means operable upon cessation of grid current flow in said input circuit for actuating said switching means and thereby automatically disconnecting said first vibratile element from said circuit and connecting said second element thereto.

.3. In an oscillator circuit, a vacuum tube having anode, cathode and control electrodes, an input circuit between said control electrode and cathode including a mechanical vibratile element, an output circuit between said anode and cathode, switching means for connecting said element to said input circuit, a second vibratile element and means responsive to cessation of current flow in said input circuit for controlling the actuation of said switching means for connecting said second element to said input circuit, and means for indicating the position of said switching means.

4. In an oscillator, a vacuum tube having anode, cathode and. control electrodes, a pair of piezo-electric crystal elements, switching means comprising a relay for connecting in one position one of said elements and in another position said other element to said control electrode, a coil for actuating said relay in one position, a circuit for connecting said coil effectively in series between said control electrode and cathode, whereby it is energized by the current flow in said circuit produced/upon generation 'of oscillations by said tube, and spring means for actuating said relay in the other'position upon deenergization of said coil.

5. In anosci1lator, a vacuum tube having anode, cathode and control electrodes, a pair of piezo-electric crystal elements, switching means comprising a relay for'connecting in one position one of said elements and in another position said other elements to said control electrode, a coil for actuating said relay in oneposition, a circuit for connecting said coil effectively in series between said control electrode and cathode, whereby it is energized by the current flow in said circuit produced upon generation ,of oscillations by said tube, spring means for actuating said'relay in the other position upon deenergization of said coil, and a pair of indicator lights one of which is energized by one position of saidrelay and the other by the other position thereof.

6. In an oscillatona vacuum tube having anode, cathode, and control electrodes, a pair of piezo-electric crystal elements, switching means comprising a relay of slow-release characteristics for connecting in one position one of said elements and in another position said other element to said control electrode and cathode,- a coil for actuating said relay in one position, a circuit for connecting saidcoil effectively in series between said control electrode :and cathode, whereby it is energized by the current flow in said circuit produced upon generation of oscillations by said tube, spring means for actuating said relay in the other position'upon deenergization of said coil, and an auxiliary circuit for said relay includinga source of current for energizing said coil, a condenser and resistor network in series with said supply and said coil, for energizing said .coil momentarily, the slow-release characteristic of said relay in cooperation of saidsupply'circuit being utilized to maintain energization of said relay prior to the generation of oscillations and during such time as required for initiating current flow in said input circuit, a switch in the energizing circuit for removing the automatic transfer feature to permit adjustments of the output circuit when desired.

ASHLEY P. BOCK. 

